1. Field of the Invention
The present invention relates to a method of manufacturing an opto-electric hybrid board in which an optical waveguide and electrical wiring are combined, and to an opto-electric hybrid board obtained thereby.
2. Description of the Related Art
Recently, information and communications using light as a medium have come into widespread use. An opto-electric hybrid board in which an optical waveguide and electrical wiring are combined (see, for example, Japanese Patent Application Laid-Open No. 2001-7463) has accordingly been employed as a substrate for use in electronic devices for information and communications and the like.
In general, this opto-electric hybrid board is structured such that an electrical wiring board including electrical interconnect lines (conductors) formed in a predetermined pattern and an optical waveguide including cores (optical interconnect lines) formed in a predetermined pattern and serving as a passageway for light are stacked together. An example of the opto-electric hybrid board is shown in FIG. 3. The opto-electric hybrid board B shown in FIG. 3 has a multi-layer structure having two layers in which an optical waveguide β is formed on an electrical wiring board α. In the above-mentioned electrical wiring board α, a plurality of electrical interconnect lines 96 are buried in an insulation layer 95 and are also supported by another insulation layer 94 in that state. In the above-mentioned optical waveguide β, a plurality of cores 93 are buried in an over cladding layer 97 and are also supported by an under cladding layer 92 in that state.
In the method of manufacturing the above-mentioned conventional opto-electric hybrid board B, however, the process of producing the optical waveguide β is performed after the process of producing the electrical wiring board α, and each of the processes involves the need for a multiplicity of steps. Thus, it takes a long period of time to manufacture the opto-electric hybrid board B. For example, the patterning of the electrical interconnect lines 96 in the electrical wiring board α involves the need for a large number of steps such as the steps of patterning a resist through exposure, development and the like, plating other portions than the resist, and then removing the above-mentioned resist. The patterning of the cores 93 in the optical waveguide β also involves the need for a large number of steps such as exposure, development and the like.
Additionally, the above-mentioned conventional opto-electric hybrid board B has the two-layer structure in which the optical waveguide β is stacked on top of the electrical wiring board α. Thus, the above-mentioned conventional opto-electric hybrid board B is disadvantageous in reducing the thickness thereof, and cannot respond to recent requests for the reduction in thickness.